IIRC (based on hard SF laser defece discussions) there is no perfect mirror, so pump enough MW/GW into it, even just for a short burst and the thing will start

IIRC (based on hard SF laser defece discussions) there is no perfect mirror, so pump enough MW/GW into it, even just for a short burst and the thing will start to melt or outright vaporize from the bit that it will always absorb. Then it won't be so shiny anymore, absorbing even more energy and so on, until it stops being a solid object. As for erratic flight paths - a physical object can't aim to match the beam steering capabilities of a group based stationary laser, given any realistic currently available propulsion or steering technology. It would need to do crazy high g & high energy manufacturing yet from the PoV of the laser its moving just a couple degrees if at all. As unlike a physical interceptor the laser beam moves at the speed of light and thud the point of aim can more more or less instantaneously.